-new stages: maybe one for each unique character, though depending on who's chosen, I'm not sure if we'd get a new Fire Emblem or Pokemon stage.
-new modes: Boss Rush (fight through a gauntlet of bosses with healing in between), All-Star Mode (a proper one this time), and Boss Rematch mode (fight individual bosses to practice)
-new bosses: Sephiroth (Final Fantasy VII), Rugal Bernstein (King of Fighters), the Immaculate One (Fire Emblem: Three Houses), Death Egg Robot (Sonic) and Gruntilda (Banjo-Kazooie), with new spirits to go along with Sephiroth (normal and One Winged Angel), the Immaculate One, the Death Egg Robot, and Rugal. (I would have gone with Geese for the SNK boss, but he uses a lot of counters, and from what I recall, you can't grab bosses)
-new Assist Trophies: Futaba, Slime, Mumbo Jumbo, Geese Howard, Rhea, Dr. Coyle, Creeper, Mallow, Ayane, Nero, Hubert, Magolor, Kazuya Mishima, Globox, Dr. Cortex, Papyrus, Henry
-new areas in Subspace Emissary:
- an SNK area (containing matches against Terry, Heihachi, and Min Min, along with some of their related spirits, along with a boss fight against Rugal)
- Midgar (Cloud's match is moved here, while a fight with Impa takes its place in the Zelda area; some new Final Fantasy spirits, matches against Cloud, Hero, Sans, and Joker, and a boss fight with Sephiroth)
- Garreg Mach Monastery (matches against Byleth and Edelgard, and the Three Houses spirits, along with a boss fight with The Immaculate One)
- Gruntilda's Lair. (matches against Banjo-Kazooie, Crash Bandicoot, and Steve, and the related spirits, along with a boss fight against Gruntilda)
Other newcomers will be spread throughout pre-existing areas, down newly-added side paths. (ex. Travis in the city, Bandanna Waddle Dee in Gourmet Race, Liquid Snake in the area where you unlock Snake, etc.)
-new songs and spirits tied to the new fighters, if necessary, along with some new Final Fantasy spirits. (ideally, covering a variety of games in the series, rather than just FF7)
-new Mii costumes tied to the fighters, especially the ones that come from new series
-make Hazardless an option on the Stage Select screen, rather than having to go through the options menu
-Palutena's Guidance for all of the playable characters